1. Technical Field
The present invention relates to a cordless communication apparatus configured to communicate by switching a communication mode between a single-slot mode and a multi-slot mode.
2. Related Art
There is known a cordless communication apparatus such as telephone equipment for executing wireless communication between a main telephone and a cordless handset. Typically, a communication between the main telephone and the cordless handset is executed such that the communication mode is switched between a single-slot mode which is for communicating by using one time slot in one frame which is divided into a plurality of time slots (i.e., a single-slot mode), and a multi-slot mode which is for transmitting identical information by using a plurality of time slots in the case of poor communication conditions. An example of such a cordless communication apparatus is disclosed in Japanese Patent Provisional Publication No. HEI 11-308123.
FIGS. 7A and 7B show an exemplary frame format showing a configuration of frames used for executing transmission and reception of data between the main telephone and the cordless handset. According to FIGS. 7A and 7B, 40 denotes a frame format of the main telephone and 41 denotes a frame format of the cordless handset. Each frame has four slots (TX1-TX4) in the transmission side, and four slots (RX1-RX4) in the reception side. One of the four slots for transmission is used for making a telephone call and one of the four slots for reception is used for receiving a call. When a slot *1 is used as a call slot, slots *2-*4 become open slots which are to be used for communication including communication of control data. A communication according to a frequency-hopping spread spectrum technology is executed by changing the channel (frequency) to be used with respect to each frame. Therefore, a channel (frequency) used in an N-th frame (frame N) is different from a channel (frequency) used in an (N+1)-th frame (frame N+1).
In the case of a single-slot mode, transmission is executed using one of the transmission slots (e.g., TX1) in the N-th frame, and reception is executed using one of the reception slots (e.g., RX1). In the case of a multi-slot mode, transmission is executed using one of the transmission slots (e.g., TX1) in the N-th frame and also using the transmission slots (e.g., TX2) in the (N+1)-th frame for transmitting the same information, and reception is executed using one of the reception slots (e.g., RX1) and also using another one of the reception slots (e.g., RX2) which is in the (N+1)-th frame for receiving the same information.
After received the two slots, one of the data which is lower in the error rate, which is judged by comparison of each bit error rate of the slots, is to be converted into audio data to output. Therefore, the multi-slot mode enables precise communication even in poor communication conditions such as in a weak electric field. It should be noted, however, the multi-slot mode has a drawback in that power consumption in the multi-slot mode is larger than that of the single-slot mode, that may shorten available time of the cordless handset which uses batteries.